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Evolution

By babyruguy Apr 16, 2014 1652 Words
Elephants Growing Smaller or No Tusks at All
As you can see from the title, the evolutionary topic I chose was Elephants. Now, it is not just the elephant its self I will be ranting on about, but the fact that, “In the last 150 years, the world’s elephant population has evolved much smaller tusks” (Chris et.al 2007). If not smaller tusks, then they have actually been growing no tusks whatsoever. Now why on earth would elephants start to evolve this way? Tusks are such an important aspect to an elephant when it comes to self-defense, mating rights, and being able to get food. If you ask me, it seems crazy that elephants would go through such a dramatic change over the last century and a half. Another crazy thing is that it usually takes thousands of years for an animal to develop evolutionary changes like the elephant has done, but the elephant has done it in 150 years? Well, scientists call this rapid evolution and it is all due to one very common problem (Environmental News Network et.al 2008).

What I was able to find out though was that this evolutionary change is actually helping them survive. How you may ask? Well, one problem in today’s world that we all know about is poaching. Poaching has had a huge effect on many animals, but the biggest on the species of the elephant. Now, elephants are not just being killed for the fun of it, but for their tusks. The tusks on an elephant are made of ivory, which is what the poachers are after because of the selling price. Ivory prices in 2007 reached $850 per kilogram (Elephant Encyclopedia et.al 2013). These tusks are not very light either, so poachers are making thousands of dollars for each tusk. Now that elephants are growing smaller or no tusks at all, it is decreasing the rate of poaching. It has not decreased drastically yet, but if this keeps happening, then poaching numbers will drastically drop over the years.

Poaching of elephants for their tusks was officially banned in 1989. Even though poaching has been illegal now for twenty-four years, it has not stopped locals in Africa from their ways of living for over thousands of years. It is very unfortunate that elephants are still being poached, but it is also how a lot of these people make their living and helps support their family. They do not understand the problem of poaching; it has been a ritual for them for so long that it is very tough to get them to stop. The only way to get these natives to stop their poaching is to show them an alternative way to make money and support their families. Type of Evolutionary Change

There are two types of evolutionary change: Divergent and Convergent. Divergent evolutionary change is the evolutionary pattern in which two species gradually become increasingly different. Convergent evolution takes place when species of different ancestry begin to share analogous traits because of a shared environment or other selection pressure. The type of evolutionary change we are dealing with when it comes to the elephants and losing their tusks is a divergent change. The reason being is because the growing of smaller tusks or no tusks at all has only been going on for 150 years so it is relatively new. So, not all elephants are being exposed to this mutation. Also, because of how new it is people will argue that you cannot really tell what type of a change it is, but from the looks of it, it is definitely the start of a divergent evolutionary change.

Type of Selection
The idea of natural selection was put forth by Charles Darwin and Alfred Russel Wallace. Natural selection is the change in allele frequency over time based on the alleles impact on reproduction and survival. There are three types of selection that an organism can be classified under. The first one is Positive Selection- This increases the frequency of the favorable allele in an organism. Then there is a Negative Selection- This decrease the frequency of the deleterious allele. Finally, there is a Balancing Selection- The allele stays at intermediate frequency in a population and has a heterozygote advantage. For the elephant, it has a positive selection. Therefore, the allele frequency favoring the elephants has been on a rise in the recent years. The growing of smaller or no tusks is a positive selection because it is starting to slow down the effects of poachers. The recent change in the allele frequency causing elephants tusk size to differ is a mutation believe it or not. Not all mutations are negative to organisms though. There are three different types of mutations: Deleterious (negative consequences), Neutral (no effect on an organism), and Advantageous (happens in DNA, changes protein, and has a positive effect). The type of mutation that elephants with decreasing size of tusks have is an advantageous one in this case because of poaching. One could argue that it could also be a deleterious mutation because they are losing a huge part to their mating rights, self-defense, and a tool to be able to get food. In this case though, the change in the allele frequency with the tusks has actually been helping the survival of these elephants. These mutations can also be put under two different categories: Somatic (body cells) (not part of gene pool so will not be passed down) and Germ-line (sex cells) (will be passed down to offspring). This change is considered germ-line because it is only being passed down to the offspring by the elephants that have the mutation. It cannot be somatic because it is not a part of the gene pool (all of the alleles in a certain species) and it is not found in the body cells of the organism.

Research Being Done
The studies and research being done by scientists is absolutely incredible. Scientific researchers, Karpagam Chelliah and Raman Sukumar, from the Centre for Ecological Sciences at the Indian Institute of Science in Bangalore wanted to study which factors gave fighting male elephants the best competitive edge. The two factors that they studied were tusks, musth, or b. Musth is a sexual state for the male elephant where their testosterone levels rise causing them to dribble urine and secrete a tar-like substance from the sides of their head. They found a population of elephants in the Kaziranga National Park in eastern India that had all these factors including males with tusks and no tusks. They call tusk less male elephants “makhnas.” There are approximately 1,165 elephants in this population. The researchers spent 458 days in the park studying all of their activities and were able to witness, and capture onto film, 116 instances where males would interact with one another. When the results were gathered they found out that out of 86 interactions between elephants where at least one was in musth, 84 of those times the male in musth won the interaction (Sekar et.al 2013). When the interaction was between normal tusked males and males that were tusked or not tusked in musth, the normal tusked males only won about 66% of the time. So, drawing conclusions from this data, I can see that it really depends on whether the male is in musth or not to see who wins the fight and can defend themselves more effectively. It is not so much the tusks that do it but the musth. In fact, Chelliah had this to say: “Most of the contests are settled without tactile contact, and physical aggression is almost non-existent among elephants. When musth males win, they don’t even have to fight. Just being in a state of musth is enough – other males retreat on just smelling the musth male. So when majority of the contests are settled without even tactile contact – tusk has hardly a role as a weapon.” That tells me that the evolutionary change is not really affecting the tusk less elephants, or “makhnas” in a bad way. For this population of elephants it really just depends on the whether one is in musth or not. This makes you wonder if this is actually the case for all populations of elephants. Now, you could agree with all the information I have given or disagree because its still very early in the evolutionary change right now, but the fact of the matter is these elephants are finding a new way to adapt and to survive out in the wild. The poaching numbers have started to decrease because the tusk size is just too small and the ivory in the tusk would not even be worth taking or the tusks are not even on the elephants. This proves the change to be part of positive selection and an advantageous mutation. Some will actually try and call this a deleterious negative mutation because the elephant is losing a key tool, but this adaptation is actually helping them to survive and therefore helping them be able to pass down this mutation to their offspring. Also, this adaptation is a divergent evolutionary change because we cannot say that all species of elephants have the mutation for this adaptation. The reason for this being is because the mutation is germ-line. Only sexual interactions between elephants that have the mutation can pass it down to their offspring. Personally I do not think that this evolutionary adaptation will result in speciation later on down the road. I think that elephants are too closely related to each other in order for two different species to be made. It is not like fish or any other type of animal that can’t mate with a different species of that animal. Now, sure the populations do have geographic barriers blocking them, but they should always be able to mate because they all have similar mating behaviors and similar sex organs. I just cannot see speciation happening with elephants.

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